WASHINGTON (REUTERS, NYTIMES) - US President Donald Trump on Tuesday (Oct 3) said the gunman in Sunday's mass shooting in Las Vegas was "a very, very sick individual" but declined to call it domestic terrorism and said gun laws would be discussed later.

"We will be talking about gun laws as time goes by," Trump said, without giving specifics, as he prepared to leave Washington for hurricane-battered Puerto Rico.

Democrats hoped the tragedy would spur congressional action on gun control. "What Congress can do - what Congress must do - is pass laws that keep our citizens safe," Sen. Chuck Schumer, D-N.Y., said on the Senate floor on Monday. But Republicans gave no indication that they would pursue gun safety legislation.

Asked if the shooting was an act of domestic terrorism, Trump added: "He was a sick man, a demented man. Lot of problems, I guess, and we're looking into him very, very seriously."

The president, who is scheduled to visit Las Vegas on Wednesday, also praised the speed of the police response there.

"What happened is, in many ways, a miracle," he said.

As Las Vegas began the process of recovering from one of the deadliest mass shootings in US history, one question hung heaviest over the city on Tuesday: Why?

The authorities have yet to provide a motive for Stephen Paddock, 64, who killed at least 59 people and injured more than 520 others on Sunday when he unleashed a rapid-fire hail of bullets on an outdoor music festival.

Armed with at least 23 firearms, Paddock, who police have described as a "lone gunman," stationed himself in a 32nd-floor luxury suite of the Mandalay Bay Resort and Casino and fired into a crowd of thousands of people.

As investigators sketched a portrait of Paddock, a wealthy gambler and amateur golfer, survivors have described the scene of carnage in vivid detail: Thousands of concertgoers screaming and running for cover as the gunman's victims fell around them. Police found Paddock dead in his room at the hotel. Investigators were still combing through his background.

Federal authorities said there were no indications that Paddock had ties to any international terrorist organisation, despite a claim of responsibility by the Islamic State in Iraq and Syria. Marilou Danley, a woman described by police as Paddock's "companion" and a person of interest in the hours after the attack, has been cleared by authorities. Danley, an Australian citizen, was not in the United States at the time of the attack.

At least 23 firearms, including a handgun, were found in Paddock's hotel suite, according to the Las Vegas Metropolitan Police Department. Sheriff Joseph Lombardo of the Police Department said Paddock used multiple rifles during the attack. A federal law enforcement official earlier said two rifles were outfitted with scopes and set up on tripods in front of two big windows. Another official said that among the weapons were AR-15-style assault rifles.

Both officials spoke on the condition of anonymity because they were not authorised to divulge details of the investigation.

Lombardo said that Paddock brought at least 10 suitcases into his hotel room over a period of time. The sheriff said that Paddock fired through his hotel room door at security guards, striking one in the leg. The guard is still alive, he said.

SWAT officers went in after the guard was shot. In addition to the weapons at the hotel, the sheriff said the police retrieved 19 firearms, as well as explosives, several thousand rounds of ammunition and "electronic devices" from Paddock's home in Mesquite, Nevada.

Who Was the Gunman?

Paddock, 64, was described as a high-flying gambler who lived in a quiet retirement community and played golf. Officials said he had no significant criminal history and drew little attention to himself.

Investigators are trying to piece together his financial history to search for clues that could help determine what set him off. Details about Paddock's career and livelihood were sparse, aside from observations by neighbours and family members that he routinely gambled large amounts of money.

"He was a wealthy guy, playing video poker, who went cruising all the time and lived in a hotel room," a brother, Eric Paddock, said. Paddock and his three brothers were raised by their mother, who told the children their father had died when in fact he was in prison, Eric Paddock said.

Stephen Paddock's father was convicted in 1961 of committing a series of bank robberies and was sentenced to 20 years in prison. He escaped from La Tuna federal prison in Texas in 1968 and became a used-car dealer and bingo parlor operator in Oregon.

The family moved around the country, from Iowa to Tucson to Southern California, another brother, Patrick Paddock II, said. In an interview with CBS, Eric Paddock said that his brother Stephen was "not an avid gun guy at all."

"The fact that he had those kind of weapons is just - where the hell did he get automatic weapons?" he asked.